1. Field of the Invention
The present invention relates to a driving mechanism of a light intercepting member.
2. Description of the Related Art
In a known lens shutter type camera, a light intercepting member, such as a shutter which opens and closes a photographing aperture, or a diaphragm which restricts the aperture diameter, is driven by a motor. The opening state of the light intercepting member is detected by a pulser (encoder), provided in a gear train through which the drive force of the motor is transmitted, or by directly detecting the position of the light intercepting member using an optical sensor. However, there is a possibility that the operation state of the gear train does not accurately correspond to the angular position of the light intercepting member due to backlash of the gears, etc. Consequently, if the detection mechanism is provided on the motor side, a slight deviation in the opening and closing timing of the light intercepting member from the correct timing could occur. In general, the light intercepting member is made of a plurality of light intercepting blades (sectors). Therefore, if the number of the light intercepting blades is increased, it is difficult to employ a detection mechanism in which the positions of the light intercepting blades are directly detected, due to spatial restriction.
Moreover, a lens barrier is used as a light intercepting member, which is opened and closed using reciprocal movement of the lens barrel in the optical axis direction. In this type of opening and closing mechanism, a drive force transmission system between the moving mechanism of the lens barrel and the light intercepting member is complicated, thus resulting in difficulty in determining the correct opening and closing timing of the light intercepting member.
The present invention provides a light intercepting member driving mechanism which can be made small, and in which the freedom of design of the arrangement of a detecting device for detecting the opening state of a light intercepting member is less restricted and the opening state of the light intercepting member can be correctly detected.
For example, in an embodiment, a light intercepting member driving mechanism is provided, including a plurality of light intercepting members, each of the light intercepting members being rotatable about a rotational axis parallel with an optical axis to open and close a photographing aperture; a drive ring which engages with the light intercepting member to open and close the light intercepting member in accordance with the angular displacement of the drive ring in forward and reverse directions about a rotational axis coincident with the optical axis; a motor which rotates the drive ring in the forward and reverse directions; a position indication portion provided on the drive ring to indicate the angular position of the drive ring; and a stationary detector which detects a passing of the position indication portion when the drive ring is rotated. The opening state of the light intercepting member is detected by the stationary detector and the position indication portion.
The position indication portion can include a slit plate having at least one through-slit, provided on the drive ring, and the stationary detector can include a photo-interrupter having a light emitter, and a light receiver opposed to the light emitter, on opposite sides of the slit plate. In this case, the photo-interrupter detects the passing of the slit of the slit plate by using the light emitter and the light receiver.
It is desirable for the slit plate to protrude in a direction parallel to the rotational axis of the drive ring; and for the light emitter and the light receiver of the photo-interrupter to be located on the outer and inner diameter sides of the slit plate.
The position indication portion can include a light reflection portion (and a non-reflection portion) provided on the drive ring, and the stationary detector can include a photo-reflector having a light emitter and a light receiver, opposed to the light reflection portion (and the non-reflection portion). In this case, the photo-reflector detects the passing of the light reflection portion by using the light emitter and the light receiver.
The light intercepting member can include a plurality of shutter sectors.
The drive ring can include a gear which is coaxial to the rotational axis of the drive ring, wherein a gear train is provided between the motor and the gear of the drive ring. The light intercepting member driving mechanism can include a first unit which supports the light intercepting members and the drive ring, and a second unit which supports the motor, the gear train, and the stationary detector; wherein when the first and second units are combined, the gear train engages with the gear of the drive ring, and the position indication portion of the drive ring and the stationary detector are adjacent to each other.
In another embodiment, a light intercepting member driving mechanism is provided, including a plurality of light intercepting members, each of the light intercepting members being rotatable about a rotational axis parallel with an optical axis to open and close a photographing aperture; a drive ring which engages with the light intercepting members to open and close the light intercepting members in accordance with the angular displacement of the drive ring in forward and reverse directions about a rotational axis coincident with the optical axis; a rotation mechanism which rotates the drive ring in the forward and reverse directions; a position indication portion provided on the drive ring to indicate the angular position of the drive ring; and a stationary detector which detects a passing of the position indication portion when the drive ring is rotated. The opening state of the light intercepting members is detected by the stationary detector and the position indication portion.
The rotation mechanism can include a motor; a gear provided on the drive ring, the gear being coaxial with the rotation axis of the drive ring; and a gear train provided between the gear of the drive ring and the motor.
The light intercepting members can be provided in a movable lens barrel which is movable in the optical axis direction. The rotation mechanism rotates the drive ring in the forward and reverse directions in accordance with the movement of the lens barrel in the optical axis direction.
The present disclosure relates to subject matter contained in Japanese Patent Application No. 2001-81611 (filed on Mar. 21, 2001) which is expressly incorporated herein in its entirety.